A data processing apparatus may be provided with data caching capability, so that data items do not need to be retrieved from memory each time they are accessed, but rather are temporarily stored locally whilst they are frequently accessed, and as a consequence the latency associated with the memory access is largely avoided. A data cache may be provided to support the data processing activities of just one component of a data processing apparatus (and is sometimes referred to as a “level 1” cache) or may be provided to support the data processing activities of a number of components of the data processing apparatus (and is sometimes referred to as a system cache).